Method of forming low-resistance metal pattern, patterned metal structure, and display devices using the same

ABSTRACT

Disclosed herein is a method of forming low-resistance metal pattern, which can be used to obtain a metal pattern having stable and excellent characteristics by performing sensitization treatment using a copper compound before an activation treatment for forming uniform and dense metal cores, a patterned metal structure, and display devices using the same.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/833,542, filed on Aug. 3, 2007, which claims priority to KoreanPatent Application No. 10-2007-0020168, filed on Feb. 28, 2007, and allthe benefits accruing therefrom under 35 U.S.C. §119, the content ofwhich is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of forming a low-resistancemetal pattern, a patterned metal structure and display devices using thesame, and, more particularly, to a method of forming low-resistancemetal pattern, which can be used to obtain metal pattern having stableand excellent characteristics by performing sensitization treatmentusing a copper compound before activation treatment to form uniform anddense metal cores, a patterned metal structure, and display devicesusing the same.

2. Description of the Related Art

As electronic devices gradually become miniaturized and increasinglyintegrated, the pattern width decreases so that the resistance of metalpattern increases, which causes signal delayed, thereby deterioratingthe display quality of the electronic devices. Accordingly, the problemscan become significant obstacles to the development of TFT-LCDs havinghigh image quality and large areas. In order to realize high-speed andhighly integrated electronic devices and products, copper (Cu), whichhas lower electric resistance and higher charge mobility thanconventional aluminum, molybdenum and chromium, and thus is able toovercome the delay of driving signals (RC delay), is useful as a patternmaterial to produce such devices and products. Copper has low specificresistance and excellent electromigration resistance. Attempts todevelop various novel technologies that take advantage of thecharacteristics of copper are continuously being made.

In electronic devices, such as integrated circuits (“IC”), liquidcrystal display devices (“LCD”), and the like, metal patterns, which areformed on a substrate, are gradually being miniaturized to accommodatethe increase in the degree of integration required in such devices fromthe miniaturization of these devices. To form metal micropatterns on asubstrate by a conventional method, a metal pattern is formed bysputtering the entire surface of a substrate with metal, forming apattern thereon by a photolithography process using a photoresist, andthen etching the exposed metal to form a metal pattern, and removing thephotoresist.

Since these conventional methods of forming a metal pattern needexpensive equipment and use methods such as a sputtering method whichmust be performed at a high temperature, the number of such processingsteps that are required and the investment cost for manufacturing thenecessary equipment are each high, which increases the overallmanufacturing cost.

However, among the methods of forming copper pattern, an electrolessplating method which plates a metal film by the reaction of a reductantand an oxidant in solution to provide the metal at the surface of anactivated substrate. Advantageously, since the electroless platingmethod is simultaneously performed over the entire substrate, themanufacturing cost is low, processes are simple, and productivity ishigh.

In the electroless plating method, since a metal film is directly platedon a diffusion-preventing film using an electrochemical method, anymicrostructures located at the interface between the diffusionpreventing film and the metal film, reactions occurring on theinterface, and the like, have an influence on all of the characteristicsof the metal pattern provided thereby, including electrical properties,thermal stability, and the like. Further, in an exemplary electrolessplating method, catalyst metal cores are formed on a lower conductivepattern film by activating the lower conductive pattern film before theformation of the plated metal layer. Since the catalyst metal corescatalyze the plating process, the plating process can thus be readilyperformed. Accordingly, a technology for forming uniform and densecatalyst metal cores in an activation process is an important aspect ofthe technology for forming a stable plated layer having desirablequalities through the electroless plating process.

To perform an activation process when the electroless plating isconducted on an insulating film, methods of performing sensitizationtreatment using SnCl₂ are known. These methods are performed for thepurpose of increasing the uniformity and density of metal cores formedby the activation process.

However, a plated film formed by activation treatment performed usingtin and palladium has insufficient adhesion to the substrate, and thusit is unsuitable for practical use.

BRIEF SUMMARY OF THE INVENTION

Accordingly, the present invention has been made to overcome the aboveproblems of the prior art, and in an embodiment, a method of forminglow-resistance metal pattern is provided, which can be used to obtain anelectroless plated layer having stable and desirable characteristics byperforming sensitization treatment with a copper compound beforeactivation treatment to form uniform and dense metal cores in theprocess of forming a metal pattern using an electroless plating method.

In another embodiment, a low-resistance metal pattern is provided whichcan provide a plated layer having stable and desirable characteristics.

In another embodiment, a display device including the metal pattern isprovided.

In an embodiment, a method of forming a low-resistance metal pattern isprovided, in which the metal pattern is formed by forming a plurality ofmetal cores by performing sensitization treatment of the substrate witha copper compound, activating a surface of the sensitized substrate, andforming a plated layer on the activated surface of the substrate.

In a further embodiment, the method can include forming a lowerconductive pattern film on a surface of an insulated substrate,performing a sensitization treatment on a surface of the lowerconductive pattern film with a copper compound, activating thesensitized surface of the substrate to form a multi-layered catalystfilm comprising a plurality of catalyst metal cores thereon, and formingone or more plated layers on a surface of the activated multi-layeredcatalyst film.

To accomplish the above, in another embodiment, a patterned metalstructure is provided, including a substrate, a lower conductive patternfilm formed on a surface of the substrate, and an upper conductivepattern film formed on a surface of the lower conductive pattern filmopposite the substrate, wherein the structure includes a seed layerincluding both a copper compound and a palladium compound, disposedbetween the lower conductive pattern film and the upper conductivepattern film.

The patterned metal structure can include a lower conductive patternfilm layered on a surface of a substrate, a seed layer including acopper compound and a palladium compound, formed on a surface of thelower conductive pattern film opposite the substrate, and an upperconductive pattern film formed on a surface of the seed layer oppositethe lower conductive film.

To accomplish the above, in an embodiment, a display device includes thepatterned metal structure. In particular, the patterned metal structurecan be applied to the construction of a liquid crystal display devicesuch that the liquid crystal display device comprises the patternedmetal structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a flow chart of the method of forming low-resistance metalpattern according to an exemplary embodiment;

FIG. 2 is a flow chart of the process of forming an exemplary lowerconductive pattern film by the method of forming low-resistance metalpattern according to an embodiment;

FIG. 3 is a schematic sectional view of the structure of the exemplarylow-resistance metal pattern according to an embodiment;

FIG. 4 is a schematic sectional view of an exemplary liquid crystaldisplay device according to an embodiment;

FIG. 5A to 5F are plan and side SEM (scanning electron microscope)micrograph showing the exemplary metal pattern film obtained in eachstep of Example 1;

FIG. 6 is a side SEM micrograph showing the exemplary metal pattern filmobtained in Example 1;

FIG. 7A to 7 c are views showing the results of measuring the adhesivityof the exemplary copper pattern obtained in Comparative Examples 1 to 3;

FIG. 8 is a view showing the result of measuring the adhesivity of theexemplary copper pattern obtained in Example 1;

FIG. 9 is a graph showing the change in thickness of plated layersdepending on reaction time in the exemplary copper pattern obtained inExample and Comparative Examples;

FIG. 10 is a graph showing the change of specific resistance dependingon the thickness of plated layers in the exemplary copper patternobtained in Example and Comparative Examples; and

FIG. 11 is the X-ray diffraction spectra of the exemplary copper patternobtained in Example and Comparative Examples.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be described in detail withreference to the attached drawings.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element or interveningelements may be present therebetween. In contrast, when an element isreferred to as being “disposed on” or “formed on” another element, theelements are understood to be in at least partial contact with eachother, unless otherwise specified. Terms such as “upper”, “lower”,“between”, and the like are labels provided to show relative positionsof elements relative to one another, and should not be construed asabsolute positions.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The use of the terms “first”, “second”, and the like do notimply any particular order but are included to identify individualelements. It will be further understood that the terms “comprises”and/or “comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

In the drawings, like reference numerals in the drawings denote likeelements and the thicknesses of layers and regions are exaggerated forclarity.

Reference now should be made to the drawings, in which the samereference numerals are used throughout the different drawings todesignate the same or similar components.

A method of forming low-resistance metal pattern, in which the metalpattern is formed by forming a plurality of metal cores by activatingthe surface of a patterned substrate and then forming a plated layerthereon, which includes performing sensitization treatment of thesurface using a copper compound before the activation treatment of thesensitized substrate.

FIG. 1 is a flow chart of the method of forming low-resistance metalpattern, and FIG. 2 is a flow chart of the process of forming a lowerconductive pattern film.

Referring to FIG. 1, in a method of forming a low-resistance metalpattern, a lower conductive pattern film 101 is formed on a surface ofan insulating substrate 10. This lower conductive pattern film is formedby patterning a metal thin film 20 on the substrate 10. A copper seedlayer 30 is formed on the metal thin film 20 opposite substrate 10 toform the lower conductive pattern film 101, and thereby sensitizationtreatment of the metal thin film 20 is performed. Subsequently, thesensitized substrate is activated using a palladium compound, to providea palladium seed layer 40 layered on a surface of the copper seed layer30 opposite the metal thin film 20, to form a plurality of catalystmetal cores. The catalyst metal cores constitute a multi-layeredcatalyst film 102 having two or more layers. For example, when thesensitization treatment is performed using a copper compound and theactivation treatment is performed using a palladium compound, atwo-layered catalyst film, consisting of a copper catalyst film and apalladium catalyst film, can be formed. Finally, the low-resistancemetal pattern 103 can be formed by forming one or more plated layers 50on a surface of the activated multi-layered catalyst film 102 oppositethe substrate 10.

Hereinafter, each step will be described in more detail with referenceto FIGS. 1 and 2.

(i) Forming a Lower Conductive Pattern Film

A lower conductive pattern film may be formed according to generalmethods of forming metal pattern film. In an exemplary embodiment, inFIG. 2, a metal thin film (metal catalyst film) 220 is first formed on asurface of a substrate 210.

The substrate material that can be used is not limited, but a plasticsubstrate or a glass substrate is desirably used as the substrate 210.

Metal thin film materials that can be used to form a lower conductivepattern film include, but are not limited to, molybdenum, nickel,copper, titanium, tantalum, tungsten and alloys thereof. The metal thinfilm may be deposited to a thickness of about 5 to about 500 nm.

Subsequently, a photosensitive film 230 is formed on a surface of themetal thin film 220 by applying a photoresist composition thereon. Thephotosensitive film 230 is selectively UV-exposed using a photo mask240, developed, and thus patterned to form a photoresist pattern 231. Inthis case, usable photoresist compositions, exposure conditions and thelike are not limited. The metal catalyst 220 that is exposed in theopened regions 232 of the photoresist pattern 231 are etched to exposethe underlying surface of substrate 210 and create a metal catalystpattern 221 using an etchant, and subsequently, the photosensitive filmcomprising the photoresist pattern 231 remaining undesirably over themetal catalyst pattern 221 is removed. For the etching process, in anembodiment, an etchant whose main component is nitric acid, hydrochloricacid, phosphoric acid, acetic acid or hydrogen peroxide may be used.

(ii) Sensitization Treatment

Electroless plating proceeds by autocatalytic nucleation and growth, andrequires seeds, i.e., small metal particles, to initiate a reaction toplate the metal. Since most metals cannot themselves function as theirown catalysts, it is necessary to form metal cores for the growth ofmetal by performing sensitization and activation treatment before metalcan be deposited by electroless plating.

When the lower conductive pattern film is formed, sensitizationtreatment of the surface of the lower conductive pattern film isperformed by use of a copper compound. In this case, the copper compoundcan be, but is not limited to, copper, a copper alloy, copper sulfate,or copper chloride.

The sensitization treatment can be performed by immersing the lowerconductive pattern film into a sensitization solution that includes thecopper compound. In an exemplary embodiment, 0.01 M to 0.1 M aqueouscopper sulfate can be used for the sensitizing solution. Thesensitization treatment may be performed at a temperature of about 20 toabout 80° C. for about 5 to about 100 seconds. When the sensitizationtreatment is completed, the lower conductive pattern film can be washedusing deionized water in order to remove the remaining sensitizationsolution.

Before the sensitization treatment, the lower conductive pattern filmcan be pretreated using an acid solution, such as nitric acid, or thelike, to increase the contact between the metal catalyst of the lowerconductive pattern film and the copper thin film formed by thesensitization treatment, by selectively increasing the roughness of thesurface of the lower conductive pattern film. In an exemplaryembodiment, an aqueous solution of 10 to 30% (v/v) of nitric acid isused.

Copper seeds are formed on the lower conductive pattern film by thesensitization treatment process, thereby increasing the number ofnucleation sites available in the activation treatment process, which isa post-process. Accordingly, the density and uniformity of the metalcores provided after treatment using the activation treatment processcan each increase, thereby improving the characteristics, such aselectrical conductivity, adhesivity and the like, of the plated layerformed thereon through the subsequent electroless plating process.

(iii) Activation Treatment

After the sensitization treatment, activation treatment is performed onthe sensitized layer to form an active layer for plating on the surfaceof metal cores. Generally, the activation treatment is performed byimmersing the sensitized pattern film into an activation solutioncontaining an activation treatment metal, such as palladium, at aboutroom temperature for a predetermined time of, in an embodiment, 5 to 200seconds. Upon activation treatment, a plurality of metal cores that actas a catalyst surface, are formed on the surface of the lower conductivepattern film, thereby providing a suitable surface on which to performthe electroless plating process.

The activation solution can include a palladium compound, such aspalladium, a palladium alloy, or palladium chloride. The activationsolution further comprises a solvent, such as for example, sulfuricacid, hydrochloric acid, hydrogen peroxide, or the like, but not limitedthereto. In an embodiment, concentration of palladium compound in thesolution is 1 to 100 mg/L. When the activation treatment is completed,the lower conductive pattern film may be washed using deionized water inorder to remove the remaining activation solution.

When the sensitization and activation treatments are performed, metalcores are formed as a multi-layered catalyst film. These metal coresserve as catalysts for accelerating the growth of metal crystals in thesubsequent plating process.

(iv) Forming a Plated Layer

A low-resistance metal pattern is then fabricated by forming one or moreplated layers on a surface of the activated multi-layered catalyst filmby an electroless plating process. In the plating step, metal crystalsare grown from the plurality of metal cores formed on the lowerconductive pattern film, thereby forming a metal pattern on a surface ofthe patterned activated multi-layered catalyst film. That is, the metalcores formed on the lower conductive pattern film aggregate with eachother during growth of the crystals, and thus form islands, and theseislands in turn combine with each other during further growth, therebyforming a continuous plated film.

During plating, a multi-layered metal pattern may be formed by growingtwo or more kinds of metals sequentially in a stepwise method. Thisplating treatment can be performed using either a wet electrolessplating method or a wet electrolytic plating method.

Herein, when the sensitization treatment is performed using a coppercompound and the activation treatment is performed using a palladiumcompound, the resulting metal pattern film having particles of palladiummetal deposited at the surface of the metal pattern film has sufficientcatalyst activity to accelerate the growth of crystals by a platingprocess, performed using an electroless plating solution, therebyproviding a more precise metal pattern on the metal pattern film.

As a metal used for plating, Cu, Ni, Ag, Au, or alloys thereof can beselectively used depending on the use of the metal pattern. In order toobtain a highly conductive metal pattern, it is preferred that a coppermetal compound solution or a silver metal compound solution be used.

Electroless plating or where desired, electrolytic plating, can beperformed using conventional commonly known methods. For example, copperelectroless plating is described below. The copper plating is performedby immersing the activated lower conductive pattern film into a platingsolution containing 1) a copper salt, 2) a complexing agent forsuppressing liquid phase reaction by forming a ligand with copper ions,3) a reductant for reducing copper ions, 4) a pH adjuster formaintaining a suitable pH to oxidize the reductant, 5) a pH buffer, and6) a modifier, for a predetermined time.

Specifically,

1) The copper salt may include, but is not limited to, copper chloride,copper nitrate, copper sulfate, or copper cyanide. In a specificembodiment, copper sulfate is used as the copper salt.

2) The reductant includes NaBH₄, KBH₄, NaH₂PO₂, hydrazine, formalin, ora polysaccharide such as glucose. In a specific embodiment, formalin ora polysaccharide such as glucose is used as the reductant.

3) The complexing agent includes a chelator such as an ammonia solution,acetic acid, guanic acid, a salt of tartaric acid, ethylenediaminetetraacetic acid (“EDTA”), Rochelle salt and the like, or an organicamine compound. In a specific embodiment, a chelator such as EDTA, asalt thereof, or the like is used as the complexing agent.

4) The pH adjuster can include an acidic compound such as, for example,H₂SO₄, or a basic compound such as, for example, sodium carbonate orsodium hydroxide, and 5) the pH buffer can include various organic acidssuch as formic acid or acetic acid, and weakly acidic inorganiccompounds such as ammonium acetate or ammonium sulfate.

6) The modifier is a compound for improving the coating and flatnesscharacteristics of a plated layer, and includes surfactants such as forexample poly(ethylene glycol) polymers, or poly(ethyleneglycol-propylene glycol) copolymers, and adsorptive materials such asfor example bis(3-sulfopropyl)disulfide, 3-mercapto-1-propane sulfonicacid, 2-mercaptopyridine, 4-mercaptopyridine, and the like, foradsorbing components that suppress the growth of crystals.

Where an electrolytic plating method is used for growing copper metals,the plating can be performed by immersing the lower conductive patternfilm into a plating composition containing 1) a copper salt, 2) acomplexing agent, 3) a pH adjuster, 4) a pH buffer, and 5) a modifier.

Herein, an annealing process can be performed if desired in order toremove water remaining in low-resistance metal pattern obtained byforming a plated layer and to improve the electrical properties andadhesivity of the plated layer. The annealing process may be performedin a nitrogen, argon or vacuum atmosphere at a temperature of about 40to about 400° C. for about 15 to about 120 minutes.

Further, after the formation of the plated layer, a protective layer canbe formed to protect the low-resistance pattern. The protective layercan be formed of nickel or a nickel alloy.

In the method disclosed herein, patterns are formed and etched by vacuumdeposition and photolithography only in the step of forming a lowerconductive pattern film. Subsequently, the lower conductive pattern filmis plated by a wet plating technology, which is a wet film formationtechnology, in which the processing cost is lower than that of vacuumdeposition technology, thereby decreasing the total manufacturing cost.Further, in the wet film formation technology, since a film is formed inan aqueous solution, the temperature for the film formation is 100° C.or lower, and thus energy consumption is lower than for a dry filmformation technology. Further, when the substrate being coated with afilm is large, fewer restrictions on equipment are encountered comparedto in the dry process, so that large metal pattern can be easily formedon a variety of substrates of different sizes.

In another embodiment, a patterned metal structure having excellentelectrical properties, adhesivity, and processability is provided. Thepatterned metal structure includes a substrate, a lower conductivepattern film formed on a surface of the substrate, and an upperconductive pattern film formed on a surface of the lower conductivepattern film opposite the substrate, wherein the structure includes aseed layer, including a copper compound and a palladium compound,disposed between the lower conductive pattern film and the upperconductive pattern film.

FIG. 3 is a schematic sectional view of a patterned metal structureaccording to an embodiment. The patterned metal structure according toan embodiment can in general include a lower conductive pattern filmlayered on a surface of a substrate 10, a seed layer, including a coppercompound and a palladium compound, formed on a surface of the lowerconductive pattern film opposite the substrate 10, and an upperconductive pattern film formed on a surface of the seed layer oppositethe lower conductive film. Specifically, in FIG. 3, the lower conductivepattern film is prepared by forming a metal thin film 20 on a surface ofsubstrate 10, and the seed layer can include a combination of a copperseed layer 30 formed on a surface of metal thin film 20 oppositesubstrate 10, and a palladium seed layer 40 formed on a surface ofcopper seed layer 30 opposite metal thin film 20. The upper conductivepattern film, formed on a surface of the seed layer (i.e., palladiumseed layer 40 in the present embodiment), corresponds to plated layer50.

In the patterned metal structure, the metal thin film 20 is formed of aconductive material selected from the group consisting of molybdenum,nickel, copper, titanium, tantalum, tungsten, and alloys thereof.Meanwhile, the plated layer 50 forming the upper conductive pattern filmcan include, but is not limited to, a conductive material selected fromthe group consisting of nickel, copper, silver, gold and alloys thereof.

A seed layer placed between the lower conductive pattern film and anupper conductive pattern film includes a copper compound and a palladiumcompound. The seed layer can include a copper seed layer 30 whichincludes a copper compound, and a palladium seed layer 40 which includesa palladium compound. The copper compound constituting the copper seedlayer 30 may be selected from the group consisting of copper, a copperalloy, copper sulfate, and copper chloride; and the palladium compoundconstituting the palladium seed layer 40 may be selected from the groupconsisting of palladium, a palladium alloy, and palladium chloride; butare not limited thereto.

The patterned metal structure can further include a protective layer(not shown), which is composed of nickel, a nickel alloy, or the like,formed on a surface of the upper conductive pattern film opposite theseed layer to protect the upper conductive pattern film.

In the patterned metal structure, the combination of strong adhesivityof the copper seed layer and the improved uniformity of the palladiumseed layer provide the patterned metal structure with a low specificresistance of about 3.0 μΩ/cm or less, so that the structure has highelectroconductivity and improved gloss, and the adhesivity of a platedfilm is improved.

The patterned metal structure can be used for various display devices,such as liquid crystal display (“LCD”), plasma display panels (“PDP”),electro luminescent displays (“ELD”) and electrochromic displays(“ECD”), as well as flat sensor such as X-ray imaging device, and thelike. In particular, where the patterned metal structure is used forliquid crystal displays, advantages realized include reducedmanufacturing costs of the liquid crystal display, and large-sizedliquid crystal displays can be manufactured.

Generally, a liquid crystal display device includes gate lines formed ina transverse direction, data lines formed in a longitudinal directionthat intersect the gate lines, and thin film transistors that are formedat intersections of the gate lines and the data lines. Pixel electrodesconnected with the thin film transistors through drain contact holes areformed in pixel regions, which are defined as the intersecting regionsof the gate lines and the data lines. The thin film transistor includesgate electrodes branching from the gate lines, a semiconductor layercovering the gate electrodes, source electrodes which overlap both endsof the semiconductor layer at regular intervals and branch from the datalines, and drain electrodes which are spaced apart from the sourceelectrodes and connect the pixel electrodes with the thin filmtransistor.

FIG. 4 is a schematic sectional view of a liquid crystal display deviceincluding the patterned structure of an embodiment. As shown in FIG. 4,the liquid crystal device according to the embodiment includes atransparent substrate 11; gate electrodes 12 formed on a surface of thesubstrate 11; a gate insulating film 15, formed on a surface of the gateelectrodes 12 opposite substrate 11; and a semiconductor layer 17,formed on the surface portion of the gate insulating film 15 coveringthe gate electrodes 12. Source electrodes 32 and drain electrodes 34,spaced apart from each other at intervals (not shown in thecross-sectional view of FIG. 4), are formed on the semiconductor layer17, and channels 33 are formed in the gaps between the source electrodes32 and the drain electrodes 24. The semiconductor layer 17 includes anactive layer 17 a formed of pure amorphous silicon (a-Si), and an ohmiccontact layer 17 b formed of impure amorphous silicon (n+a-Si) andplaced on a surface of the active layer 17 a. A protective layer 27,having drain contact holes 28 for partially exposing the drainelectrodes 34, is formed in the upper portion of the thin filmtransistor, and pixel electrodes 40 connected with the drain electrodes34 through the drain contact holes 28 are formed in pixel regionslocated in the upper portion of the protective layer 27. The liquidcrystal display device is not limited to this structure, and can bevariously modified, added to and substituted by those skilled in theart.

Hereinafter, exemplary embodiments of the invention will be described indetail with reference to Examples. Here, these Examples are set forth toillustrate the invention, but should not to be construed as limitingthereto.

EXAMPLES Example 1

Molybdenum was deposited to a thickness of 50 nm on a glass substrate,and then the glass substrate, with the molybdenum thin film so formed,was spin-coated with an AZ1512 photoresist (Clariant Corp. positive tonephotoresist). Subsequently, the photoresist-coated glass substrate wasexposed through a photo mask using broadband UV exposure (equipmentmanufactured by Oriel Corp.) as a light source for 7 seconds so that theoutput of broad band UV resulted in a dose of 13 mJ/cm² in the exposedregions defined by the photomask, and was developed using a TMAHdeveloper and patterned and the exposed molybdenum thin film etchedusing AT10 (manufactured by Dongwoo Fine-Chem Co. Ltd.) as an etchant,thereby obtaining a lower conductive pattern film.

800 ml of deionized water was added to a 1.5 L vessel, 5.99 g ofCuSO₄.5H₂O was added thereto, and the mixture was then stirred.Subsequently, 26.99 g of EDTA.4Na was added thereto and stirred, and7.47 ml of HCHO (37 wt % aqueous solution) was added thereto. Next, thepH of a plating solution was adjusted to 12.6 using sodium hydroxide(NaOH), and 5 ml of a 2,2-dipyridyl solution was then added thereto, toprepare a sensitization solution having the composition shown in (a) ofthe following Table 1. The sensitization solution was bubbled andsimultaneously heated to a temperature of 60° C. After the bubbling andheating of the sensitization solution was stopped, the lower conductivepattern film was immersed into the sensitization solution for seconds,removed therefrom, and washed with water. FIG. 5A to 5B show plan andside SEM micrograph of the resulting sensitized metal pattern film.

A 2 l beaker was filled with 1 L of deionized water, 2 ml of conc. (aq.)HCl, and then 0.03 g of PdCl₂ was added thereto and stirred thoroughlyuntil dissolved, to prepare the palladium activation solution having acomposition shown in (b) of the following Table 1. This activationsolution was stirred for about 1 hour, and was then introduced into acopper electroless double boiling apparatus, and then the sensitizedpattern film obtained in the previous step was immersed therein for 60seconds.

FIGS. 5C and 5D show plan and side SEM micrograph of the metal patternfilm, activated for 10 seconds, and FIGS. 5E and 5F show plan and sideSEM micrographs of the metal pattern film, activated for 60 seconds.Referring to FIG. 5A to 5F, it can be seen that metal cores weresparsely formed on the lower conductive pattern film during the firststage, but grew when the activation treatment was performed, so thatthey combined with each other to form a continuous thin film.

The metal pattern film so obtained was immersed into an electrolesscopper plating solution having the composition shown in (c) in thefollowing Table 1 at a temperature of 65° C. for 5 minutes, so thatcopper metal crystals were grown on the lower conductive pattern film,thereby obtaining a copper pattern film.

FIG. 6 showed a side SEM micrograph of the obtained metal pattern filmplated with copper. As shown in FIG. 6, it can be seen that the platedfilm so obtained does not exhibit separation at the interface, and hashigh adhesivity.

TABLE 1 (a) (b) Pd activation (c) Copper Sensitization solution solutionplating solution Deionized water 800 ml Deionized water 1 l Coppersulfate 3.5 g CuSO₄•5H₂O 5.99 g Conc. hydrochloric Salt of tartaric acidEDTA•4Na 26.99 g acid 2 ml 8.5 g HCHO (37 wt %) 7.47 ml PdCl₂ 0.03 gFormalin (37%) 22 ml 2,2-dipyridyl solution Thiourea 1 g 5 ml Ammonia 40g

Comparative Example 1

A copper pattern film having a predetermined pattern was obtained as inExample 1, except that the activation treatment was not performed usinga palladium compound, and only the sensitization treatment wasperformed. The material properties of the copper pattern film soobtained were evaluated, and the results thereof are given in thefollowing Table 2.

Comparative Example 2

A copper pattern film having a predetermined pattern was obtained as inExample 1, except that the sensitization treatment was not performed,and the activation treatment was performed using only the palladiumactivation solution used in Example 1. The material properties of thecomparative copper pattern film so obtained were evaluated, and theresults thereof are given in the following Table 2.

Comparative Example 3

A copper pattern film having a predetermined pattern was obtained as inExample 1, except that a tin chloride solution (a mixed solution of 10g/L SnCl₂ and 40 ml/L of conc. HCl (37 wt % aq.) in water) was used as asensitization solution instead of an aqueous copper sulfate solution.The material properties of the comparative copper pattern film soobtained were evaluated, and the results thereof are given in thefollowing Table 2.

Experiment Example 1 Measurement of Adhesivity

In the patterned metal structure (thickness 4500 Å, width 7 μm) obtainedin Example 1, the adhesivity of the plated layer was tested by tape pulltest using adhesive tape, and the results thereof are shown in FIG. 8.Meanwhile, the adhesivity of the plated layer obtained in ComparativeExamples 1 to 3 was evaluated, and the results thereof were shown inFIG. 7A to 7C.

As shown in FIGS. 7A to 7C and 8, in the case of Comparative Example 1,the adhesivity of a plated layer was good, but the specific resistanceof the plated layer was undesirably high since Cu₂O was formed on theplated layer. In the case of Comparative Example 2, in which only theactivation treatment was performed using palladium, it was found thatthe adhesivity of the plated layer was insufficiently low, so that theplated layer completely peeled off when the adhesive tape adheredthereto was pulled to separate it from the plated layer. Meanwhile, inthe case of Comparative Example 3, in which a tin compound was used as asensitizing agent and the activation treatment was performed using apalladium activation solution, the adhesivity was somewhat improvedcompared to Comparative Example 2, but was insufficient compared toExample 1. That is, in the case of Example 1, in which a copper compoundwas used as a sensitizing agent and the activation treatment wasperformed using a palladium compound, the adhesivity of the plated layerwas best.

Experimental Example 1 Measurement of Specific Resistance

The specific resistances of each of the metal pattern film obtained inExample 1 and Comparative Example 1 to 3 were measured at thicknesses ofboth 300 nm and 450 nm, and the results thereof are given in Table 2.The thickness thereof was measured using a Surface profiler P-10,manufactured by Tencor corp., and the specific resistance thereof wasmeasured using a 4 point probe. The change in the thickness of a platedlayer was measured by observing the change in the reaction time inExample 1 and Comparative Example 1 to 3, and the results thereof areshown in FIG. 9. Further, the change in the specific resistance of aplated layer was measured depending on the thickness thereof, and theresults thereof are shown in FIG. 10.

TABLE 2 Specific resistance Specific resistance (μ ohm-cm) (μ ohm-cm)Thickness of plated Thickness of plated Examples layer 300 nm layer 450nm Peeling test Comparative 3.0 2.8  0/140 Example 1 (Cu) ComparativeMeasurement Measurement 88/140 Example 2 impossible impossible (Pd)Comparative 2.9 2.4 69/140 Example 3 (Sn/Pd) Example 1 2.6 2.5 24/140(Cu/Pd)

As shown in Table 2 and FIGS. 9 to 10, the growth rate of the copperelectroless plated layer in Example 1 was similar to that in ComparativeExamples 1 to 3. However, the specific resistance in Comparative Example1 was the highest, and the specific resistance in Comparative Example 2,in which the plated layer includes palladium, was similar to that ofExample 1. In the case of Comparative Example 2, in which the activationtreatment was performed using a palladium compound, the specificresistance of the plated layer could not be measured due to a strongpeeling phenomenon.

FIG. 11 is a graph showing the results of X-ray diffraction analysis ofcopper pattern films obtained in Example 1 and Comparative Examples 1and 3. As shown in FIG. 11, in the case of Comparative Example 1, sincecopper oxide (CuO₂) peaks exist at a 2Θ of 36.6° (111) and 42.5° (200),and copper (Cu) peaks exist at a 2Θ of 43.3° (111) and 50.5° (200), itis predicted that the plated layer includes Cu₂O in addition to Cu.However, in the case of Comparative Example 3 and Example 1, in whichthe activation treatment was performed using palladium, the oxide peaksdid not exist.

As seen in the above results in which, at the time of electrolessplating, a copper compound was used as the sensitization agent and apalladium compound was used as the activation agent, the adhesivity andspecific resistance of the plated film prepared thereby were found toprovide the best results.

According to the method of forming metal pattern, a low-resistance metalpattern can be obtained efficiently by a wet film formation processwithout undergoing a conventional sputtering process, which requireshigh-temperature and high-vacuum conditions. Accordingly, the presentinvention can be used to reduce equipment investment and manufacturingcosts. Moreover, the method of forming metal pattern can also be appliedto a flexible substrate, and the metal pattern can be continuouslyproduced by a roll-to-roll process, thereby significantly improvingproductivity.

The metal pattern has improved adhesivity and specific resistance forthe plated layer relative to a plated layer prepared without thesensitization treatment using a copper compound and the activationtreatment of the substrate, so that the reliability and pricecompetitiveness of display devices using the patterned metal structureof the present invention can also be improved.

As described above, although the preferred embodiments of the presentinvention have been disclosed for illustrative purposes, those skilledin the art will appreciate that various modifications, additions andsubstitutions are possible, without departing from the scope and spiritof the invention as disclosed in the accompanying claims.

What is claimed is:
 1. A method of forming a metal pattern, in which themetal pattern is formed by forming a plurality of metal cores by:performing sensitization treatment of a surface of a substrate with acopper compound, activating the sensitized surface of the substrate byactivation treatment of the substrate, and forming a plated layer on theactivated surface of the substrate, and wherein the method comprises:forming a conductive patterned film on a surface of an insulatedsubstrate; performing sensitization treatment on the conductive patternfilm by immersing the conductive pattern film into a sensitizationsolution including the copper compound to form a sensitized patternfilm; activating the sensitized substrate by immersing the sensitizedpattern film into an activation solution containing palladium, apalladium alloy, or palladium chloride to form an patterned activatedmulti-layered catalyst film comprising a plurality of catalyst metalcores thereon; and forming one or more plated layers on the surface ofthe patterned activated multi-layered catalyst film.
 2. The method offorming metal pattern according to claim 1, wherein forming theconductive pattern film comprises: forming a metal thin film on asurface of the insulated substrate; forming a photosensitive film on asurface of the metal thin film opposite the insulated substrate;patterning the photosensitive film by selectively exposing anddeveloping the photosensitive film using a mask; and etching the exposedunderlying regions of metal thin film in the patterned photosensitivefilm.
 3. The method of forming metal pattern according to claim 1,wherein the copper compound is copper, a copper alloy, copper sulfate,or copper chloride.
 4. The method of forming metal pattern according toclaim 1, wherein forming a plated layer is performed using a wetelectroless plating method or a wet electrolytic plating method.
 5. Themethod of forming metal pattern according to claim 1, wherein, informing a plated layer, a metal for plating is selected from the groupconsisting of Ni, Cu, Ag, Au, and alloys thereof.
 6. The method offorming metal pattern according to claim 1, wherein forming a platedlayer is performed by immersing the sensitized and activated conductivepattern film into a copper electroless plating solution including acopper salt, a complexing agent, a reductant, and a pH adjuster.
 7. Themethod of forming metal pattern according to claim 2, wherein the metalthin film is formed of a conductive material selected from the groupconsisting of molybdenum, nickel, copper, titanium, tantalum, tungsten,and alloys thereof.
 8. The method of forming metal pattern according toclaim 1, further comprising forming a protective layer on the platedlayer.
 9. The method of forming metal pattern according to claim 8,wherein the protective layer comprises nickel or a nickel alloy.
 10. Themethod of forming metal pattern according to claim 1, further comprisingannealing a metal pattern after the formation of the metal pattern byforming a plated layer.
 11. The method of forming metal patternaccording to claim 10, wherein annealing is performed under a nitrogen,argon or vacuum atmosphere at about 40 to about 400° C. for about 15 toabout 120 minutes.